1. Field of the Invention
The present invention relates to a lubricating oil filling structure for an engine, and more particularly to a lubricating oil filling structure suitable for a horizontally opposed engine for an aircraft.
2. Description of the Background Art
FIG. 8 shows a part of a horizontally opposed engine in which a cylinder block 106 is attached with a cylinder head 107 and is further covered by a cylinder head cover 108, a filler tube 111 having one end attached on the upper surface of the cylinder head cover 108 and the other end extending upward. FIG. 9 shows another horizontally opposed engine, in which a service hole 122 for inserting a piston pin 129 for connecting a piston 127 and a connecting rod (not shown) is formed on the side surface of the cylinder block 106, and is adapted to be closed by attaching a hole cover 113 by a bolt 114 thereon after connection. The engine provided with a similar service hole is disclosed, for example, in JP-A-2001-193401, the entirety of which is hereby incorporated by reference.
When the filler tube 111 is mounted as in the background art shown in FIG. 8, it is necessary to form a special mounting hole on the cylinder head cover 108 and fix the filler tube 111 on the cylinder head cover 108 with a clamping ring 140 attached at the end of the filler tube 111. In addition, in the case of the horizontally opposed engine shown in FIG. 9, the service hole 122 has to be covered by the hole cover 113. Therefore, the number of required man-hours and the number of components undesirably increase with the arrangements of the background art.
When the filler tube 111 is mounted on the cylinder head cover 108 as in the background art of FIG. 8, e.g., in the case of the horizontally opposed engine, the filler tube 111 is positioned at the distal end in the widthwise direction (widthwise direction when it is mounted on the vehicle body or on the air frame and the like) as shown by a phantom line in FIG. 2. Therefore, as shown by the phantom line in FIG. 2, the upper end interferes with the cowl for covering the engine in the arrangements of the background art. In order to avoid such interference, it is necessary to bend the filler tube significantly or to locally deform the cowl to make a projection.
If the engine is intended to be mounted on an aircraft in which improvement of aerodynamic properties is required, the cowl is required to cover around the engine with a smooth and continuous curved surface, while simultaneously avoiding local deformation of the cowl. Since there exist components of an induction system in the vicinity of the cylinder head even when the filler tube is bent, there are many restrictions in disposing the filler tube at a position where interference with those components may be avoided and good operability may be achieved. In addition, when the filler tube is disposed in the vicinity of the output shaft, the filler tube must be positioned away from moving or rotating parts such as the propeller. Accordingly, various layouts for parts and equipment may be necessary.